In this application, star-shaped polymers based on thermoplastic biodegradable hydrogels (TBH) will be synthesized. These new polymers possess characteristics that allow for controllable biodegradability, hydrophilicity and thermoplasticity. The polymers can be fabricated into microspheres either in solution with a choice of nontoxic solvent or by a heat melt process. In addition, the smaller hydrodynamic volumes of degraded products which results from the star shape of polymers is advantageous for effective renal clearance. The synthesized polymers are polyethylene oxide (PEO)/polylactic acid (PLA) and PEO/polycaprolactone (PCL) star-shaped block copolymers. The merit of this molecular architecture has been demonstrated in the preliminary studies. Polymer microspheres will be characterized before and after loading of protein drugs. The protein drugs, leuprorelin, human growth hormone (hGH) and bone morphogenic protein (BNV-2) will be loaded in the polymer microspheres. The proteins serve as model drugs as well as potential therapeutic proteins once the proposed studies are successfully completed. The designed microspheres can also be utilized for broad ranges of protein drugs. After in vitro, in vivo release studies and biocompatibility evaluation, the obtained results will provide valuable information which is necessary for the preclinical studies toward the possible human application with novel delivery concepts of therapeutic protein drugs.